PICTURE a river in Washington, D.C. - no doubt you thought of the Potomac. But the city has another river, the Anacostia, which flows from the Maryland suburbs through eastern Washington before meeting the Potomac, some two miles south of the White House.

While the Potomac is known as the setting for many of Washington's most popular attractions, the Anacostia is actually omitted from most tourist maps.

Mayor Anthony Williams has called it "Washington's forgotten river." The Anacostia's eastern shore is home to some 200,000 Washingtonians, many of them African-American. The west shore holds a mix of industrial, residential and recreational facilities.

On Saturday nights, gay bars draw crowds to a group of former warehouse buildings. After the bars empty out, churches fill up. The west side of the river is also home to a popular fish market; the Arena Stage, a nonprofit theater; a military museum at the Washington Navy Yard; and the hulking Robert F. Kennedy Memorial Stadium.

Still, much of the west shore is undeveloped, underdeveloped or simply down and out.

Now the city has begun a 20-year, $8 billion plan to revitalize the Anacostia's banks. "Growth is going to happen, and we want to make sure it results in a great waterfront," said Andrew Altman, who until last year was Washington's planning director. Mr. Altman now heads the quasi-public Anacostia Waterfront Initiative.

The most eagerly awaited part of the plan may be the new baseball stadium for the Washington Nationals, in what is now a seedy industrial neighborhood at the end of South Capitol Street. The Nationals will play at nearby R.F.K. Stadium until 2008, when the new ballpark is expected to open. The architect of the stadium will be announced in the next week, Mr. Altman said.

Another focus is the neighborhood called Near Southeast, where Kathryn Gustafson, of Seattle's Gustafson Guthrie Nichol (best known for the Princess Diana memorial in London), has been chosen to design a 1.8-acre park. The site, Mr. Altman said, is now a "glass-strewn parking lot."

Eight hundred public housing units near the park are about to be torn down and replaced with 1,600 homes, some subsidized and others market rate. The federal Hope VI program, which supports replacing distressed public housing with mixed-used communities, is financing the project, and displaced residents will receive housing vouchers, Mr. Altman said. A new headquarters for the United States Department of Transportation, designed by the architect Michael Graves, and a hotel are also being built beside the park.

A third focus of the initiative is Washington's Southwest, which 40 years ago was one of the nation's first federally financed urban renewal areas. Rows of brick houses were demolished for concrete apartment buildings. Now, in many cases, those same buildings need renewal.

Worse, the riverfront esplanade, separated from the buildings by up to a dozen lanes of traffic, is a series of "completely failed public spaces," Mr. Altman said. "We need to start over."

When the Southwest neighborhood is completed, Mr. Altman said, "it will redefine the skyline of Washington."

But that could take time. Until January, the Federal National Mortgage Association, or Fannie Mae, the nation's largest backer of home mortgages, had been expected to move several thousand employees from Washington's pricey Northwest to the site of an outmoded mall in Southwest. A partnership including Forest City Enterprises, a developer from Cleveland, was prepared to spend some $700 million on the project, dubbed Waterfront.

But then Fannie Mae discovered accounting irregularities that threw $9 billion of its previously reported profits into question. It pulled out of the development. "Obviously, the decision was due to the accounting issues," said Alfred King, a spokesman for Fannie Mae.

But Fannie Mae's attempt to improve its financial prospects - termed a "capital recovery" - puts a different kind of capital recovery at risk. The agency's pullout "leaves us with a big hole," Mr. Altman conceded.

In this case, not everyone hates a hole. The new development would have blocked the river views that some long-term Southwest residents enjoy. "There have been some incredibly antagonistic community meetings," Mr. Altman said, noting that some people have wondered how a 10-story building could be put up by the water. "But I remind them that they're living in a 10-story building right now," he said.

To those residents, Fannie Mae's pullout, which slows down redevelopment of the neighborhood, may be welcome. David Smith, the development manager for Forest City Enterprises, said that, with Fannie Mae no longer Waterfront's lead tenant, "we are brainstorming; we are trying to determine how to go forward."

In the meantime, Arena Stage, just a couple of blocks from the Waterfront site, is moving ahead with its own $100 million expansion. A futuristic building by the Canadian architect Bing Thom will unite the two existing theater spaces and a new third one under a swoopy roof. Nearby, the National Children's Museum is planning a new building by the architect Cesar Pelli.

One thing is for sure: the new development is drawing attention to the Anacostia River.

Toni Griffin, a deputy planning director now detailed to the waterfront initiative, recalls taking a boat trip with civic leaders on the Anacostia a couple of years ago. One of the district's bigwigs - she'd rather not say who - pointed to the south and announced, "That's Virginia." In fact, it's southeast Washington, home to, among other landmarks, the Frederick Douglass National Historic Site.

Ms. Griffin was not surprised by the mistake. It was proof, she said, "of the real need for people to appreciate this resource, the river that runs through our city."

Mr. Altman agreed. "Our goal," he said, "is to put the Anacostia back on the map."